During insertion or removal of substrates from a substrate container, traces of dust, gaseous impurities, or increased humidity can be introduced into the substrate container, adversely affecting product yield of the resident wafers. Accordingly, there is an increased demand for controlling the environment within these containers during substrate handling to achieve or maintain a high level of cleanliness.
A microenvironment within a substrate container is, in some instances, purged using an inert gas that is injected into the interior of the container through an inlet port causing the air within the container to exit through an outlet port. Systems and methods of delivering purge gas into the container have been designed to provide an improved environment within the container.
As front opening unified pods (FOUPs) were developed, bottom purge ports were introduced by carrier manufacturers to enable the purging of the interior environment with clean dry air (CDA) or inert purge. These purge modules were introduced below the internal bottom surface of the FOUP shell.
When purge diffusers were introduced, it became apparent that if the diffuser was assembled axially to the purge interface it would not only interfere with the wafer handling exclusion volume but also the wafers stored inside of the FOUP. Instead, without making any modifications to the existing shell design, the diffuser tube was designed to be internally offset axially.
U.S. Pat. No. 9,054,144 to Burns et al. (“Burns”) discloses a substrate container with a purge tower that includes a base portion and a diffuser tower portion connected by an offset conduit. The offset conduit enables the tower portion to be offset toward the back of the container, thereby enabling the interior space to be better utilized for substrate storage and handling and provided a more compact design. The disclosure of Burns is hereby incorporated by reference herein except for express definitions and patent claims contained therein.